For my son's robot Halloween costume we want to run four wires for an RGB LED light in the helmet down to n Arduino that is in the main body. The helmet needs to be detachable, so I want to add a plug in these wires where he can fairly easily plug and unplug the wires going from the helmet. I have some spring wire terminals, but they take a lot of force to unplug. A couple of brainstorming ideas I had were wiring to an RJ45 connector or a JST connector. Any thought whether those ideas would be sensible for this, or what easy options are there?
I would go for the 'old' audio DIN connectors or PS2 keyboard/mouse connectors. The former are relatively heavy if you use the ones with metal housing.
I've had good results with JST connectors (particularly ones like this).
These do require a fair bit of force to unplug, given that that's their only locking mechanism. They will be able to withstand some tugging and pulling without popping out. I suppose an upside to not having clips is that with excess force, the connector will simply unplug, rather than getting the connectors or wires themselves ripped out (as I think @Paul_B indicated).
I'd probably find a JST connector easier to solder to (perhaps even to perfboard).
If you prefer RJ*, perhaps RJ9 would be better suited?
+1 for the old fashioned DIN connector that @sterretje suggested. If memory serves, they had solder pins so no fancy crimp tools required. If you have an old PC keyboard from the last century kicking about, then you can probably repurpose the curly lead from it. Digikey has some, search for SD-50. There may be others with more or less contacts.